Godot Engine - Feature-packed 2D and 3D open source game engine.
DragonRuby Game Toolkit - DragonRuby Game Toolkit is a commercial-grade, yet beginner-friendly, 2D game engine.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
DragonRuby Game Tookit - Tiny, fast and cross-platform, 2D game engine in Ruby.
Unity - The multiplatform game creation tools for everyone.
MonoGame - MonoGame is an open source implementation of the Microsoft XNA 4 Framework.